Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards, and Universal Serial Bus (USB) flash drives (e.g., thumb drive, handy drive, memory stick, flash stick, jump drive) for general storage and transfer of data between computers and other digital products. It is a specific type of Electrically Erasable Programmable Read Only Memory (EEPROM) that is erased and programmed in large blocks. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid-state storage is needed. Examples of applications include Personal Digital Assistants (PDAs) and laptop computers, digital audio players, digital cameras and mobile phones.
Flash memory is non-volatile, which means that it does not need power to maintain the information stored in the chip. In addition, flash memory offers fast read access times (although not as fast as volatile direct Random Access Memory (DRAM) used for main memory in PCs) and better kinetic shock resistance than hard disks. These characteristics explain the popularity of flash memory for applications such as storage on battery-powered devices. Another feature of flash memory is that when packaged in a “memory card”, it is enormously durable, being able to withstand intense pressure, extremes of temperature and immersion in water.
Flash memory stores information in an array of floating-gate transistors, called “cells”. In traditional single-level cell (SLC) devices, each cell stores only one bit of information. However, newer flash memory, known as multi-level cell (MLC) devices, can store more than one bit per cell by choosing between multiple levels of electrical charge to apply to the floating gates of its cells.